1. Technical Field
The present invention relates to an optical detecting device, a display device, and electronic equipment.
2. Related Art
Recently, a display device provided with a position detecting function in which a touch panel is disposed on the front side of a display section has been used in electronic equipment such as cellular phones, personal computers, car navigation devices, ticket-vending machines, and banking terminals. This display device allows a user to touch an icon or the like in a display image or input information while referring to the image displayed on the display section. Exemplary known position detecting methods using such a touch panel include resistance and capacitance types.
On the other hand, the display area of a projection display device (projector) or a display device for a digital signature is wider than that of the display device of a cellular phone or a personal computer. Therefore, it is difficult to realize position detection by using the above-described resistance-type touch panel or capacitance-type touch panel in such display devices.
Known existing technologies relating to a position detecting device used for a projection display device include, for example, the technologies disclosed in JP-A-11-345085 and JP-A-2001-142643. However, with this type of position detecting device, the system undesirably becomes large-scale. Moreover, when a detection area is wide, a detection signal from a light-receiving element such as a photodiode becomes small. This makes it difficult to obtain sufficient detection accuracy. Furthermore, to improve the detection accuracy, it is necessary to adjust an optical design parameter or a circuit design parameter. This undesirably increases design costs, production costs, etc.